I just bought a Raspberry Pi and set it up as an XBMC HD movie player and IP (catchuptv) player.
Unlike my Xbox 360 which had lots of issues playing movies, this seems to play all formats without any problem. Also setup is BBC Iplayer, ITV Player, 4OD and CH5 catchup player - all working fine.

cost of setup was about £40 in total.

by the way I know its based on a linux minipc but I thought this post topic was more relevant than the linux forum category.